1. Field of the Invention
The present disclosure relates generally to evaluating geologic formations, e.g., geologic formations surrounding a hydrocarbon recovery wellbore. More particularly, embodiments of the disclosure relate to acoustic logging tools including a housing member arranged to delay or impede the propagation of acoustic energy through the housing member.
2. Background
The use of acoustic measurement systems (e.g., audible and/or ultrasonic systems) in downhole applications, such as logging-while-drilling (LWD), measurement while drilling (MWD), and wireline logging applications, is well known. Such acoustic measurement systems are utilized in a variety of downhole applications including, for example, borehole caliper measurements, measurement of drilling fluid properties, and the determination of various physical properties of a geologic formation. In one application, acoustic waveforms may be generated at one or more transmitters deployed in the borehole. The acoustic responses may then be received at an array of longitudinally spaced apart receivers deployed in the borehole. Acoustic logging in this manner provides an important set of borehole data and is commonly used in both LWD and wireline applications to determine compressional and shear wave velocities (also referred to as slownesses) of the geologic formation.
Many acoustic logging tools include a housing member that separates a transmitter section of the tool from a receiver section of the tool. In operation, the transmitter section is actuated to emit acoustic energy into a wellbore, and the acoustic energy propagates to the receiver section along multiple paths. For example, a first acoustic signal can propagate through a geologic formation that is the subject of investigation, and a second acoustic signal can also propagate through the housing member. Since the second signal propagated through the housing member often interferes with the receipt and evaluation of the first signal propagated through the geologic formation, efforts have been made to distinguish and acoustically isolate the first and second signals.